This invention relates generally to the field of infrared temperature measurements; and, more particularly to an improved infrared thermometer having a shortened response time.
In the area of nuclear fusion, assessment of the performance of a tokamak limiter depends strongly on the thermal loads the plasma deposits on the limiter during a discharge. The best method for determining the thermal load is to measure the limiter surface temperature during a pulse. Present commercial systems which give two-dimensional information are limited either to the TV framing rate (30/sec) giving a 16 ms response time or to devices using mechanical scanning by mirrors giving a 30 ms response time. Line scanning or point systems have response times of 40 .mu.s to 100 .mu.s, but are inadequate for very non-symmetrical temperature profiles, such as on tokamak limiters. Since the two-dimensional temperature profile of the limiter surface provides very useful information about the edge properties of the plasma (e.g., scrape-off thickness and edge transport coefficients), it is desirable to obtain this information with as great a temporal resolution as possible.
Infrared radiation is a convenient non-contact means for measuring surface temperature. If the infrared emissivity of an object is independent of wavelength in the region of interest, then the true temperature of the object can be determined solely from the ratio of the radiance at two different wavelengths. This is the theoretical basis for two color pyrometry.
Since the tokamak limiter surface is usually TiC or C and emissivity is nearly constant with wavelength for these materials over the wavelength bands chosen for an infrared thermometer, two color pyrometry may be used.
Therefore, it is an object of the present invention to provide a two-dimensional infrared thermometer having a shortened response time.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention.